Species Profile: Rusty Blackbird

Troubled Blackbird of the Bog

Photo: USFWS

Once upon a time, you could, on a summer's day, count on hearing the creaky song of the Rusty Blackbird (Euphagus carolensis) filtering from the vast wetlands of the boreal forest. Decades ago, on a winter's day, one could reliably locate small flocks of Rusties foraging at the edge of the swamps in the Southern United States. Now, most of us consider it special to spot a Rusty Blackbird anywhere. The Rusty Blackbird is a species in deep, deep trouble.

Five years ago, we published a paper in Conservation Biology laying out the case for both acute short-term and chronic long-term population declines. Since then, the plight of the Rusty Blackbird has attracted only a small amount of interest. The Rusty Blackbird is now considered a species of concern in a few regions by the Fish and Wildlife Service and nationally by Partners in Flight, but unlike other species in similar dire trouble, little in the way of serious concerted research has been initiated.

As part of the northern boreal fauna, Rusty Blackbirds are not well monitored. However, they have been found on over 90 Breeding Bird Survey routes. These data, when analyzed from 1966-2001, show a remarkable but depressing (and highly statistically significant) 10.8% annual decline.

Several other lines of evidence support the hypothesis that the Rusty Blackbird is a species in severe decline. First, a systematic comparison of authoritative regional accounts of bird distribution and annotated bird checklists from the late 19th century to today reveal a consistent pattern. The species has changed from being described as almost universally common or abundant to one where even in the center of its range it is uncommon or rare.

In particular, renewed attention to the distribution and abundance of birds in the boreal forest has caused many observers to revisit areas that have hardly been explored since the days of early ornithologists. Often these modern survey crews are able to detect only handfuls of Rusty Blackbirds in areas where they were formerly common and easy to find only a half century ago. We had this experience as we explored the boreal bogs and woodlands of the Northwest Territories along the Liard and McKenzie River in we late '90s. More recently, reports from recently opened-up regions of Northern Alberta have found a similar dearth of Rusties.

Beyond the demonstrable population declines, the Rusty Blackbird has several strikes going against it. First; it is a blackbird. Blackbirds are comprised of several evolutionary clades (groups of genetically related species) of New World Icterids and are, for the most part, omnivorous and adaptable birds of open habitats. Because of these ecological characteristics, blackbirds have shown profound increases as agriculture and suburbanization spread across the American landscape. In particular, the closest relatives of the Rusty Blackbird are grackles and the Brewer's Blackbird, species whose success is linked to adapting to human development and agriculture. However; the Rusty Blackbirds' specializations have restricted it to wooded wetlands where it forages primarily on invertebrate prey.

Of all North American species, Rusty Blackbirds are the most tied to this kind of habitat. Unfortunately, not being a member of a glamorous threatened group of species, such as neotropical migratory songbirds, Rusty Blackbirds stand alone and unappreciated (except by us, of course). Finally, Rusty Blackbirds' breeding distribution is located primarily in far northern boreal bog lands where few roads penetrate, access is difficult, and few bird surveys are conducted.

What is unclear is the cause of these declines. Given the species' greater ecological specialization than its close blackbird relatives, it is tempting to assume that habitat destruction or degradation is at the root of the problem. Witness where it winters: the wooded wetlands of the Deep South, a habitat that has disappeared from some regions and is highly altered elsewhere. And, while huge tracts of boreal wetlands remain from central Canada west through Alaska, many eastern boreal habitats have suffered significant habitat loss.

Alternatively, while Rusty Blackbirds tend to forage in small groups, away from other blackbirds and grackles, they often join their evolutionary relatives at large blackbird roosts. The past lethal spraying of blackbird roosts may have contributed to their decline, if for some reason they were concentrated in the roosts most likely to be sprayed. Finally, in light of the recent West Nile Virus epidemic, the possibility that some disease has ravaged the population cannot be completely ignored. Here now is a clear case of a decline, one shrouded in so many unknowns that no clear conservation/management strategy can be championed. We hope that another five years will not slip by before a serious effort is made to study the demise of this elusive maverick of the blackbird family. You do the math - how long will it take before this species is lost if 11% of the population is lost per year?